The takeaway
CoStar Group Inc shows a pronounced seasonal pattern over 10 years of data — strongest in July (+7.1%) and softest in September (−2.8%).
Right now
In July, the stock has risen 80% of years, averaging +7.1%, about +4.9 pts better than the S&P 500.
The full picture
CoStar Group Inc's most dependable month has been July, higher in 8 of 10 years; September has been its least reliable, up just 10% of the time.
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Month by month
The stock's clearest edge over the S&P 500 lands in July (+4.9 pts); it has trailed the market most in October (−5.1 pts).
“vs S&P” is CoStar Group Inc’s average for a month minus the S&P 500’s average for that same month — isolating CoStar Group Inc’s own seasonal edge from broad market drift.
Reality check
Over the last 5 years, July has closed higher 80% of the time versus 80% across the last 10 years — the pattern is holding.
Figures are the typical (median) July return and how often it rose — the last 5 years versus the last 10(the heatmap’s default window). This verdict stays anchored to that 10-year window even if you zoom the chart, so it never disagrees with the badges above.
In plain English
Strip the year back and a single month does the heavy lifting: July, up in 8 of 10 Julys while the other eleven tend to blur together.
Its average (+7.1%) and median (+6.2%) land within a hair of each other — the tell of steady, year-after-year gains rather than one outlier doing the work. That reliability comes with real swings, mind — even July ranges by 8.2% from year to year, so any single year can land far from the average. Crucially, the gain is the stock's own rather than a rising tide's: July has cleared the S&P 500 by +4.9 points above the index. That consistency sets it apart from the field, where the average stock manages July only about 61% of the time.
The strength clusters rather than stands alone — March–August forms a firm stretch that carries much of the year. At the other end of the calendar, September has been the soft spot — the weakest of 4 months that average a loss (−2.8%), and the edge isn't year-round — the stock has trailed the S&P 500 in October, September, and December. Its roughest month on record was a −17.6% October in 2025 — a reminder of how hard even a seasonal name can fall.
Reassuringly, the tendency has held its shape: the recent five years still track the years behind them.
The takeaway is less about when to buy than what to expect: July aside, the stock's months offer little reliable tilt.
Short answers on the stock's best month (July), its worst (September), and whether it really trades seasonally.
Yes, to a pronounced degree. Since 2016 its best month (July, +7.1%) has run well ahead of its worst (September, −2.8%) — the heatmap above shows how steady that gap has been year to year.
July has been the strongest, averaging +7.1% and closing higher in 8 of 10 years since 2016.
It's the weakest, averaging −2.8% — historically a soft spot, though it still varies from year to year.
Explore
These names have the strongest July track records on record — a starting point for comparison.
Before you trade